The present invention generally relates to automotive roll control systems and, more specifically, to roll control systems which may be selectively locked and unlocked for use in selective roll control.
Various prior patents have addressed the challenges related to existing automotive roll control systems. As examples, U.S. Pat. No. 5,362,094 (the ""094 patent) discloses a hydraulic control for a stabilizer bar system. Another hydraulic system is disclosed in U.S. Pat. No. 5,749,596 (the ""596 patent). The system disclosed in the ""094 patent is effective, however, the system is also relatively complex as it requires double acting hydraulic cylinders, valves, manifold blocks and various conduit lines. The system disclosed in the ""596 patent also includes a hydraulic actuator and somewhat simplifies the system and reduces the number of required components. UK published patent application GB 2,284,184 discloses a similar roll control system using a hydraulic actuator.
Despite the improvements made in this area of technology, prior systems used to selectively apply roll control are bulky and, therefore, may not be easily incorporated in various vehicles depending on space availability. In addition, prior systems have not had the ability to control the roll axis both actively and semi-actively or to self-center the roll axis without the use of complex electronics and sensors.
For these general reasons, additional improvements are necessary in this technology relative to providing an even more compact and cost efficient system with greater capabilities.
The present invention therefore generally provides a vehicle roll control system including a torsion bar having a longitudinal axis and first and second end portions disposed generally along the longitudinal axis. A first arm or passive arm has a passive end fixed to the first end portion of the torsion bar and extends transverse to the longitudinal axis. This first arm rotates with the torsion bar. The first arm further includes an opposite end configured to be coupled to the vehicle chassis. A second arm or active arm includes an active end rotatably coupled to the second end portion of the torsion bar and extending transverse to the longitudinal axis. This second arm, in accordance with the invention, can either rotate with respect to the torsion bar or be locked for rotation with the torsion bar. The second arm also includes an opposite end configured to be coupled to the vehicle chassis.
In a preferred embodiment, an actuator is mounted to the second arm. The actuator includes a driven member movable between first and second positions with respect to the active end of the second arm. The first position allows rotation of the second arm at the active end relative to the second end portion of the torsion bar and the second position locks the active end to prevent rotation thereof relative to the second end of the torsion bar. In the preferred embodiments, the driven member moves linearly between the first and second positions and the actuator may be hydraulic, electric, pneumatic or combinations thereof. One of the driven member and the active end includes a cam surface, while the other includes a cam follower. The cam follower moves along the cam surface when the driven member is in the first position and the cam follower is locked against the cam surface when the driven member is in the second position.
More preferably, the cam follower is in a centered position on the cam surface when the driven member is in the second position and the cam follower can move in opposite, noncentered directions when the driven member is in the first position. Therefore, when the driven member is moved by the actuator to the second position, this drives the cam follower and the second arm to the centered position. In this centered and locked position, driving conditions such as cornering and non-level surfaces will twist the anti-roll bar and applies a force to the vehicle chassis that increases the overall spring stiffness between the chassis and the vehicle body, such as during corning or off-road conditions. In the first position or unlocked position of the driven member, when the anti-roll bar is twisted, little or no force is transmitted to the vehicle chassis to alter the normal spring rate of the suspension. Moreover, when one wheel is deflected relative to an opposite wheel, the actuator may be selectively actuated to drive the cam follower to the centered position thereby tending to level the vehicle between the two wheels. Additionally, the cam follower will tend to self-center along the cam surface to maintain the two arms in a level plane.
Various additional objectives, advantages and features of the invention will become more readily apparent to those of ordinary skill in the art upon review of the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.